Phendimetrazine is an amphetamine analogue that acts as a sympathomimetic with anorectic properties, used for weight loss. There is scarce information on the safety of phendimetrazine associated with fetal anomaly when used early in pregnancy. Some studies suggested that use of phendimetrazine during pregnancy may increase the risk of cleft lip and palate, and congenital diaphragmatic hernia. The aim of the study was to evaluate fetal outcomes among pregnant women who were inadvertently exposed to phendimetrazine in early pregnancy.

Total 62 singleton pregnant women who were inadvertently exposed to phendimetrazine during early pregnancy were prospectively followed up (twin pregnancy was excluded). In addition, 122 age and gravity matched pregnant women were not exposed to any potential teratogenic agent during pregnancy were recruited as controls.

Mean age of exposed women was 33.2 ± 4.9 years, with mean gravity was 2.2 ± 1.1 and mean gestational weeks at exposure was 4.2 ± 2.0. All gestations were confirmed by ultrasonography. Of exposed women, 3 (1.0%) had spontaneous abortions, 2 had artificial abortion, 23 cases were lost to follow-up and 7 cases were transferred to other hospital. Therefore, 26 pregnancies inadvertently exposed to phendimetrazine were evaluated. Two babies had abnormal outcome: one had choroid plexus cyst, another baby had bilateral equinovarus. In control group, 11 babies were born with abnormal outcome (7.7% vs. 12.0%; P = 0.54; odds ratio, 0.61; 95% confidence interval, 0.12 to 2.96).

These preliminary results suggest that phendimetrazine may not pose substantial fetal risks. Although more information is needed, there is a critical need for further research on medication used during pregnancy.